 |
Epidermal disorders
|
|
|
|
|
|
|
MRI of an acneic Hair follicle (red). Epidermis is violet.
|
|
|
Acne
is a chronic inflammatory disorder of the hair follicle/sebaceous gland unit and affecting the face, thorax and back. It typically attacks girls between the ages of 14 and 17 and boys between 16 and 19. It is a condition still affecting 5% of women over forty. The hormonal component is very important in the acne phenomenon, since the androgen balance is disturbed in 50 to 70% of girls with acne.
Acne has four major causes and consequences. - The production of sebum by the sebaceous gland is increased; - The sebaceous canal is hyperkeratinised, which leads to obstruction of the canal; - The microflora development, in particular Propionibacterium Acnes, and finally the obstruction of the canal which prevents the excretion of the sebum, causing dilation of the canal and the formation of a microcyst or comedo. These are commonly called whiteheads, when deep down, or blackheads when they are at the surface. They are formed of sebum, of the bacteria P. Acnes, and other resident flora bacteria.
It is not advisable to squeeze a blackhead, for the cyst bursting towards the dermis will produce an inflammation due to the presence of horny material, lipids and bacteria leading to the development of pustules.
|
|
|
|
Seborrhoeic dermatitis, still called seborrhoeic eczema, is a condition resulting from an excess of sebum and myosis development. It is widespread and concerns 1 to 3 % of the adult population. Oily skin is a major predisposition factor and attacks are often triggered by stress, fatigue etc. It gives a red appearance to the skin with small patches of dry skin and usually causes itching. Seborrhoeic dermatosis affects young infants particularly on the scalp, and forms what is commonly called cradle cap.
|
|
|
Freckles
|
|
|
Freckles, also called ephelides, are particularly numerous in redheads. Freckles are small coloured spots on the skin, sometimes raised, particularly noticeable on the face, the hands, and the neck. They are due to an accumulation of pheomelanin in the basal cells of the epidermis due to excessively active melanocytes, which are normal in number
|
|
|
Moles or beauty spot
|
|
|
Moles or benign pigmented nævi. This type of nævus is extremely frequent, and is considered as normal. It is a benign proliferation of melanocytes which accumulate in a mass. This type of mark appears from the second stage of childhood and persists from then on. Nævus rarely turns into a malignant melanoma.
However, any signs such as an increase in the diameter, a change of colour or the association of several colours, bleeding or itching, should be checked by a dermatologist, without delay, as the mole may be becoming a malignant melanoma.
Since mole is due to an accumulation of melanocytes, people who have a lot of moles are advised not to expose their skin to the sun. Doing so can stimulate division of the melanocytes in the mole and lead to the development of a malignant melanoma.
|
|
|
Pregnancy mask
|
|
|
Pregnancy mask or chloasma is a skin pigmentation disorder, developing during pregnancy (2nd or 3rd trimester) or during hormone treatment (oral contraceptives, hormonal supplements). The dark blotches are more or less confluent, localized on the forehead, the cheeks and sometimes the upper lip. Pregnancy mask affects 50 % of pregnant women, mainly those with a dark skin. Several pigmentation factors are involved - increase in oestrogen-progesterone hormones, UV irradiation, increase in the circulating hormone, Melanin Stimulating Hormone (MSH). These blotches normally fade spontaneously during the few months following delivery, but they may become permanent, following an excessive sun exposure during pregnancy. Women should therefore avoid to expose their skin to the sun during her pregnancy and to protect themself daily from UVA rays.
|
|
|
|
Vitiligo is a fairly widespread skin disorder affecting 1 to 2 % of the population. It is characterised by the appearance of unpigmented areas mainly on the feet, hands, and face. Depigmentation is caused by a loss of melanocytes and a reduction in Langerhans cells. Vitiligo can be difficult to tolerate psychologically. Evolution of the disorder is unpredictable. It can last for years - even for life - or just disappear. Sun exposure produces burns, then the lesions extend over a larger area or regress. Treatment is long and often disappointing. The application of cosmetics to provide colour or a local mask can be a good way of limiting the psychological effects at least partially. For extensive lesions, skin repigmentation sessions, using UVA irradiation, are prescribed, under medical supervision, since they are undertaken over a period of one or several years.
|
|
|
|
|